The invention relates primarily to the electroplating of the electrical contact surfaces of loose piece terminals with noble metal or noble metal alloys. These metals are characterized by good electrical conductivity and little or no formation of oxides that reduce the conductivity. Therefore, these metals, when applied as plating, will enhance conductivity of the terminals. The high cost of these metals has necessitated precision deposition on the contact surfaces of the terminals, and not on surfaces of the terminals on which plating is unnecessary.
Apparatus for plating is called a plating cell and includes an electrical anode, an electrical cathode comprised of terminals in strip form or loose piece terminals in contact with a separate electrical conducting member, and a plating solution; i.e., an electrolyte of metal ions. The plating solution is fluidic and is placed in contact with the anode and the terminals. The apparatus operates by passing electrical current from the anode, through the plating solution to the terminals. The metal ions deposit, as metal plating on those terminal surfaces in contact with the plating solution.
Heretofore, plating of loose piece terminals was accomplished by immersing all or a portion of the terminals in a plating apparatus such as that disclosed in U.S. Pat. No. 4,321,124. Immersing the terminal in plating solution, however, results in a layer of plating on the outside as well as the inside of the terminal. Masking of loose piece terminals requires at least one more manufacturing operation. Even if the terminals could be masked after they are stamped and formed and prior to their removal from a carrier strip, the process would be time consuming. Some immersed surfaces are difficult to mask, particularly the surfaces of small size electrical terminals.
The present invention accomplishes selective plating according to a rapid automatic process and apparatus without a need for masking immersed terminal surfaces on which plating is unnecessary. The present invention is particularly adapted for plating on the interior surfaces of the loose piece terminals, and not the external surfaces, despite contact of the external surfaces with plating solution.
U.S. Pat. No. 4,384,926, issued May 24, 1983, and U.S. Pat. Application Ser. No. 458,005, now U.S. Pat. No. 4,427,498 owned by this Assignee, disclose plating cells for selectively plating the interior surfaces of electrical terminals that are in strip form. The disclosures in the above mentioned documents are hereby incorporated by reference. The disclosures in the two documents are the subject matter of published European Patent Application No. 83301271.9, published Oct. 12, 1983 under Publication No. 0 091 209.
The present invention discloses a means whereby plating cells such as those disclosed in the above mentioned references can be used for loose piece terminals. The apparatus disclosed herein is comprised of a means for feeding loose piece terminals to a continuously rotating mandrel, a means for retaining the loose piece terminals against a portion of the rotating mandrel, a conduit for supplying plating solution through the mandrel and a source of electrical potential. The mandrel has a plurality of anode containing nozzles therein, the anodes being mounted for reciprocation into and out of the interior of the terminals that are against the mandrel. The conduit supplies plating solution under pressure through the nozzles and upon the anodes and into the interiors of the terminals in which the anodes are received. The electrical current flows from the anodes, through the plating solution and into the interiors of those terminals in which the anodes are received.
The means for retaining the loose pieces against the rotating mandrel is a resiliently mounted member which surrounds a portion of the mandrel as the mandrel rotates, whereby the loose pieces are held against the mandrel during the plating process wherein the anodes move into the interiors of the terminals, plating solution is injected over the anodes and the anodes are retracted from the terminals. The terminals are released from the mandrel after the anodes have been retracted and the terminals have passed the end of the retaining means.
A better understanding of the invention is obtained by way of example from the following description and the accompanying drawings.